Turbine blade



June 10, 1930. RAY 1,762,352

TURBINE BLADE Filed Oct. 9, 1928 )w u-- I WITNESS INVENTOR 3 i J-LRay I BY ATTORNEY Patented June 10, 1930 UNITED STATES rarnnr OFFICE JAMES L. BAY, OF SWARTHMORE, ?ENNSYLVANIA, ASSIGNOE T WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA TURBINE BLADE Application filed October 9, 1928.

My invention relates to elastic fluid turbines, and more particularly to the blading thereof, and it has for an object, to improve the construction of apparatus of this charfiacter.

Hollow turbine blades have the distinct advantage of being light in weight, as compared to solid blades, and yet being sufficiently strong to withstand the various bending and centrifugal stresses to which they are subjected during operation of the turbine. The reduction in weight of the blades not only reduces the stresses in the blades themselves, but also in the turbine rotor, for the cen- 1 trifugal stresses vary directly with the weight. Hence, the use of hollow blades permits a lighter rotor construction and in this way provides for reducing the cost of a turbine. Furthermore, in turbines having blades of the larger sizes, such as the low pressure reaction blades, the stresses for solid blades become exceedingly high, and in many cases these stresses are prohibitive. In such cases, itis desirable to use hollow blades.

Various types of hollow blades have been proposed, but in most cases such blades have either been so designed as to be very difficult to manufacture, or have been of a design which rendered the completed blade inhercntly defective.

. It is a more particular object of this invention, therefore, to provide a hollow turbine blade of relatively simple construction which may be readily and easily manufactured and which shall be practically free from inherent defects when completed.

This and other objects are effected by my invention, as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is an elevation of a turbine blade;

Fig. 2 is any transverse section of the blade shown in Fig. 1, such, for example, as a section on the line IIII of Fig. 1; and

Fig. 3 is a section showing a detail of construction.

According to my invention, a blade is formed with a cavity extending from the tip towards the base thereof to provide a hollow Serial No. 311,324.

blade section, and this cavity opens into one of the working faces of the blade, preferably the concave face, along lines which are approximately the loci of the points of intersection of the neutral axes of the various transverse sections of the blade and its concave face. A previously formed cover plate is then fitted into the opening to complete the con cave face, and this cover plate is, preferably, secured in place by fusion of metal, as by welding. In this way, the blade may be easily made, and the welds, or the like, which hold the cover plate, fall on the neutral axes of the various transverse sections, or very near to these neut al axes where there is either no bending stress, or very little bending stress.

In Fig. l of the drawing, I show a turbine blade indicated generally, at 10, and comprising a blade portion 11 and a root portion 12. The blade portion 11 may be either straight or tapered but preferably it is tapered, as shown; and it is formed with a cavity 13 extending from the tip to approximately the base thereof to provide a hollow blade section. The cavity may likewise be either straight or tapered, and I also prefer to have the cavity tapered, as shown.

Fig. 2 has been designated as a section on line 11-11 of Fig. 1, but for the purposes of illustration, Fig. 2 may be assumed to be a transverse section taken anywhere through the hollow portion of the blade 11. The line 15-15 represents the neutral axis of the section shown, that is, the line connecting the points at which there is no longitudinal stress when the blade is bent in a direction at right angles to the longitudinal extent of the section. From Fig. 2, it will be seen that the cavity 13 opens into the concave face of the blade 11 and, preferably, along lilies which are the loci of the points of intersection of the neutral axes of the various transverse sections of the blade and the concave face thereof. l Vhile I have shown the cavity 13 open-. ing into the concave working face of the blade, it will be understood that the blade may be so designed that the neutral axis 15-15 will intersect the convex face, in which case it would be advisable'to have the cavity open into the convex faces.

The opening through the concave face into the cavity 13 is closed by a suitable closure strip, or cover plate, 14, which is arranged to complete the concave face of the blade across the opening to the cavity. It will thus be seen that this blade is formed in two unitary sections, the section 16 including the convex working face as well as the inletand the outlet edge portions of the concave working face, and the other section consists of the closure strip 14. By making the blade in this manner, the section 16 may be readily forged with the cavity 13 therein, or if desired, this section may be formed as a solid blade section and the cavity machined out by a milling cutter, or other suitable tool. Likewise, the cover plate 14 may be previously die-formed, or it may be machined.

The cover plate 141 is preferably secured across the opening in the section 16 by fusion of metal such, for example, as by welding, as shown at 17. in Fig. 3, and, as the opening into which this cover plate is fitted, is defined by lines which are approximately the loci of the points of intersection of the neu tral axes of the various transverse sections, it follows that the welds, or the like, which secure the cover plate in place will fall on the neutral axes of the various transverse sections, or very near thereto, and consequently, there will either be no bending stress, or very little bending stress on the welds which hold. the cover plate 14 in place.

It will readily be seen, therefore, that I have provided a hollow turbine blade which may be either of straight or tapered construction and which may be readily formed. in sections by relatively simple machining or forging operations; and that. by arranging the sections so that they lit together along points which fall on the neutral axes of the.

transverse sections of the blade, or very near thereto, it is assured that practically no stress will fall upon the welds which hold the respective sections together.

While 1 have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically setforth in the appended claims.

7 What I claim is:

1. A turbine blade having concave and convex faces and comprising a section including one face and'the inlet and outlet edge portions of the other face, said section having a cavity extending from the tip towards the base thereof and opening into said other face along lines which are the loci of the points of intersection of said other face and a plane which includes the neutral axes of two or more transverse sections of the blade, and a closure strip fitted into the opening to close the cavity, said closure strip being arranged to complete said other face across said opening.

2. A turbine blade having concave and convex working faces and comprising a section including the convex working face and the inlet and the outlet edge portions of the concave working face, said section having a cavity extending from the tip toward the base thereof and opening into the concave working face between the respective inlet and outlet edge portions thereof, and a closure strip fitted into the opening to close the cavity, said closure strip being arranged to complete the concave working face'across said opening between the inlet and outlet edge portions.

3. A device according to claim 2 in which the closure strip is secured in place by fusion of metal.

4. A turbine blade having concave and convex faces and comprising a section including the convex face and thejnlet and the .outlet edge portions of the concave face, said section having a cavity extending from the tip towards the base thereof and opening into the concave face along lines which are approximately the loci of the points of intersection of the neutral axes of the various transverse sections and the concave face, and a closure strip fitted into the opening to close the cavity, said closure strip being arranged to complete the concave face across said opening.

5. A turbine blade having concave and convex faces and comprising a section including the convex face and the inlet and the outlet edge portions of the concave face, said section having a cavity extending from the tip towards the base thereof and opening into the concave face along lines which are the loci of the points of intersection of the concave face and a plane which includes the neutral axes of two or more transverse sections of the blade, and a closure strip fitted into the opening to close the cavity, said closure scrip being arranged to complete the concave face across said opening.

In testimony whereof, 1 have hereunto subscribed ny name this 1st day of October,

JAMES L. RAY. 

